It was "reasonable" for the officers responding to reports of gunman in front of a recreation center to believe that they were in danger when Tamir reached for what turned out to be a pellet gun, McGinty said.
While the 911 caller had told a police dispatcher that Tamir was probably a juvenile and that his weapon was likely a "fake," that information was not passed on to Loehmann or his partner, Frank Garmback, McGinty added.
Also, the airsoft-type gun Tamir was holding lacked the orange safety tip that would have indicated to Loehmann that it wasn't a real firearm, McGinty said.
"Simply put, given this perfect storm of human error, mistakes and miscommunications by all involved that day, the evidence did not indicate criminal conduct by police."
Assistant prosecutor Matt Meyer added: "To any observer, it's extremely difficult to distinguish between the real and fake gun unless you pick it up."
In addition, Tamir appeared "to be much older that he really was," Meyer said. Tamir was 5-foot-7 and 175 pounds.
But the grand jury's decision not to indict the officers was a huge disappointment to Tamir's family, and it immediately drew ire from outraged African-Americans who had been demanding justice for the boy.
"Tamir's family is saddened and disappointed by this outcome but not surprised," said one of the family's lawyers, Sasha Ginzberg.
"It has been clear for months now that Cuyahoga County Prosecutor Timothy McGinty was abusing and manipulating the grand jury process to orchestrate a vote against indictment," Ginzberg said. "Even though video shows the police shooting Tamir in less than one second, Prosecutor McGinty hired so-called expert witnesses to try and exonerate the officers."
The Rice family is renewing its request for the Justice Department to investigate the killing and urging anyone who wants to "express their disappointment" to do so peacefully, Ginzberg added.
The Justice Department is already looking into whether there were any civil rights violations
Echoing McGinty, Ohio Gov. John Kasich called Rice's death "a heartbreaking tragedy." Kasich, a Republican presidential candidate, said he understood that many would wonder whether justice was served, but he called for unity and peace on the streets.
Meanwhile, police set up barricades outside the Cleveland courthouse as a few demonstrators holding up pictures of Tamir and other blacks killed by while police officers around the country gathered nearby.
Tamir's death on Nov. 22, 2014, was caught on choppy surveillance video that stoked public outrage and prompted fresh calls for police reform.
But while his death did not lead to violent street battles in Cleveland, like the death of Michael Brown did in Ferguson, Missouri, it further fueled the debate over policing in minority communities and what would constitute a justifiable use of force. And it became a rallying point for the "Black Lives Matter" movement.
Tamir's family demanded that both officers be charged with murder and accused McGinty of dragging his feet and siding with police.
Later, it was revealed that before joining the Cleveland Police Department, Loehmann had quit the police force in the suburb of Independence after an "emotional meltdown" at the gun range.
In a November 2012 memo, Deputy Chief Jim Polak recommended that Loehmann be dismissed and questioned his ability to follow instructions and make good decisions in stressful situations.
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Corky Siemaszko is a senior writer for NBC News Digital.
Daniella Silva is a reporter for NBC News, specializing in immigration and inclusion issues, as well as coverage of Latin America.
Elisha Fieldstadt is a breaking news reporter for NBC News.